Comments

not enjoying the company, and definitely not growing on top of moss. The material I manage to collect, though, doesn’t always reflect the entire picture: the ones for this observation are from the fringe and show moss fronds sticking from under the lichen crust. But there are few pieces from the middle of the thallus, clearly showing sandy grains of sandstone as a substrate. I will stick with D.scruposus here.

Are you saying the specimen in hand is entirely growing on top of moss, and not directly on rock? The photos would seem to be precisely opposite. You can see it expanding and undercutting nearby mosses, but most of it looks to me to be nowhere near moss.

D.muscorum can definitely and often does grow entirely on top of mosses. I think it may occasionally spill over onto bare rock. Zaca would be the expert in this area, but that’s been my limited experience in western North America.

While it shows moss sticking from just under the edge of the specimen, I am not sure how much D.muscorum is supposed to associate with moss. Is it supposed to grow on top of moss, where moss completely insulates it from the rock? Then it’s definitely D.scruposus, not D.muscorum.

But I’ll definitely go along with it for this one! See how the apothecia have that distinctive eroding rim around the pit-like disk? (I don’t know how to describe it better, sorry.) This is 100% typical and characteristic of Diploschistes. Given that it’s conspicuously growing right on bare rock — not even a hint of soil or moss! — this has got to be D. scruposus.